Breath sample tube and method of making it

ABSTRACT

Indium tubes are coated inside with &#39;&#39;&#39;&#39;Carbowax 1500,&#39;&#39;&#39;&#39; and are used to encapsulate breath samples. The coating acts to passivate the indium surface preventing a decomposition reaction between the indium and any ethyl alcohol contained in the breath sample.

United States Patent 11 1 Forrester Feb. 18, 1975 [54] BREATH SAMPLE TUBE AND METHOD OF 3,103,277 9/1963 Ehrhardt et .al 206/46 R x MAKING IT 3,202,523 8/1965 Steeg 117/135 X 3,418,218 12/1968 Levy 117/135 X [75] In ento Macq o Forrester, S Louis, 3,618,394 11/1971 Penton 220/64 x [73] Ass1gnee: lntoxlmeters, lnc., St. LOUIS, Mo. Primary Examiner Morris 0. walk Filed! 1973 Assistant Examiner-Timothy W. Hagan [21] AppL NOJ 329,656 Attorney, Agent, or Firm-Polster and Polster [52] U.S. Cl 23/259, 206/.6, 128/2 C,

220/64, 117/135 [57] ABSTRACT [51] Int. Cl B011 3/00 Field of Search 23/232 R, 254 R, 259, 9 Indium tubes are coated inside with Carbowax 206/46 R, 46 V, 6 S 56 A 43 1500, and are used to encapsulate breath samples. 73/4215 422 G l The coating acts to passivate the indium surface pre- 128/ C; l17/ 35; 106/271 venting a decomposition reaction between the indium and any ethyl alcohol contained in the breath sample. [56] References Cited UNITED STATES PATENTS 6 Chims, N0 Drawings 3,063,286 11/1962 Nerheim 206/46 R X BREATH SAMPLE TUBE AND METHOD OF MAKING IT BACKGROUND OF THE INVENTION In testing breath samples, as for example in determining alcohol content for evidentiary purposes, it is desirable to be able to preserve a sample for at least hours and preferably for days or weeks. It is also desirable, when analysis is to be made by chromatographic or fuel cell sensing methods, to encapsulate a known amount of breath sample in a fusible or easily rupturable capsule.

Indium would appear to be a candidate for use as a capsule forming material. It can be fabricated into tubes which can be pressure-welded by manually operated tools, to enclose a given desired amount of breath.

However, it has been found in practice that the alcohol component in many breath samples encapsulated in indium decomposes in a short time.

BRIEF SUMMARY OF THE INVENTION In accordance with this invention, generally stated, indium tubing to be used to encapsulate breath samples containing ethyl alcohol or other breath components such as acetaldehyde, acetone or methanol, is coated on its inside wall with Carbowax (polyethylene glycol, see Merck Index, 8th Ed., page 210). In the preferred embodiment, Carbowax 1500 is used. The number suffix of the various types of Carbowax" described as operative hereinafter indicates the approximate aver age molecular weight of the polyethylene glycol. Breath samples containing ethyl alcohol, encapsulated in the coated tubes are stable and are preserved without deterioration for two weeks or more at room temperature.

It has been found that indium, in the presence of carbon dioxide, air and water, has the property .of decomposing ethyl alcohol. The treatment of the inside walls of the tubing with a dilute solution of Carbowax in a suitable solvent such as chloroform or methanol, passivates the indium. This is an unexpected property because Carbowax is itself an alcohol.

A solution of 0.1% by weight of Carbowax is sufficient to produce a marked improvement, and 0.5% provides complete protection.

In a preferred illustrative method of treating indium tubing, a tube four inches long with an outside diameter of 0.2 inch and an internal diameter of 0.14 inch is purged with n-hexane (Skellysolve B) and dried. The tube is then immersed, in such a way as to fill the tube completely, in a solution of 0.5% Carbowax l500 in methanol (w/v) at 25 i 3 C. for five minutes. removed and then dried at 65 C. for 30 minutes in room atmosphere. The tube is now ready for use.

Various other cleaning agents besides n-hexane, such as acetone, methanol and hydrochloric acid can be used. Other solvents for the (Carbowax can also be used, such, for example, as chloroform. As has been indicated, 0.5% of Carbowax 1500 provides complete passivation, but as little as 01% provides marked passivation. Other polyethylene glycols of other molecular weights can be used, polyethylene glycols ranging in average molecular weight from 600 to 2,000 (e.g., Carbowax 600, 1000, I500, I540) having been found operative.

More than 0.5% of Carbowax 1500 provides no discernably different result, and therefore is wasteful of material. Sufficient of the polyethylene glycol to pro duce the desired passivation does not interfere with the manual pressure-welding of the indium tubing to form sealed breath-holding capsules, nor does it alter significantly the volume of breath contained in the capsule as compared with that of an untreated capsule ofthe same starting dimensions.

Numerous variations within the scope of the appended claims will occur to those skilled in the art in the light of the foregoing disclosure.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

l. A capsule for receiving breath samples, comprising an indium tube, the inner wall of which is passivated with polyethylene glycol.

2. The capsule of claim 1 wherein the wall has been passivated with a solution containing at least 0.1% polyethylene glycol in a solvent.

3. The capsule of claim 2 wherein the polyethylene glycol has an average molecular weight in the range 600 to 1,540.

4. A method of passivating indium tubing with respect to ethanol comprising treating said tubing with a dilute solution of polyethylene glycol in a solvent for said polyethylene glycol.

S. The method of claim 4 wherein the inner wall of said tubing is treated with a solution of at least 0.1% weight to volume of polyethylene glycol.

6. The method of claim 5 wherein the polyethylene glycol has an average molecular weight of between 600 and 1,540. 

1. A CAPSULE FOR RECEIVING BREATH SAMPLES, COMPRISING AN INDIUM TUBE, THE INNER WALL OF WHICH IS PASSIVATED WITH POLYETHYLENE GLYCOL.
 2. The capsule of claim 1 wherein the wall has been passivated with a solution containing at least 0.1% polyethylene glycol in a solvent.
 3. The capsule of claim 2 wherein the polyethylene glycol has an average molecular weight in the range 600 to 1,540.
 4. A method of passivating indium tubing with respect to ethanol comprising treating said tubing with a dilute solution of polyethylene glycol in a solvent for said polyethylene glycol.
 5. The method of claim 4 wherein the inner wall of said tubing is treated with a solution of at least 0.1% weight to volume of polyethylene glycol.
 6. The method of claim 5 wherein the polyethylene glycol has an average molecular weight of between 600 and 1,540. 